﻿ Java - Test if a binary tree is a subtree of another

# Java: Test if a binary tree is a subtree of another binary tree

## Java Basic: Exercise-150 with Solution

Write a Java program to test if a binary tree is a subtree of another binary tree.

Sample Solution:

Java Code:

``````import java.util.*
public class Solution {
/**
* @param T1, T2: The roots of binary tree.
* @return: True if T2 is a subtree of T1, or false.
*/
public static boolean is_Subtree(TreeNode T1, TreeNode T2) {
if (T2 == null) return true; // If T2 is null, it's always a subtree (base case)
if (T1 == null) return false; // If T1 is null but T2 is not, T2 can't be a subtree

if (is_Same(T1, T2)) return true; // Check if the current subtrees are the same
if (is_Subtree(T1.left, T2) || is_Subtree(T1.right, T2)) return true; // Check left and right subtrees

return false; // If none of the above conditions match, T2 is not a subtree of T1
}

public static boolean is_Same(TreeNode t1, TreeNode t2) {
if (t1 == null || t2 == null) {
return t1 == t2; // If one of the nodes is null, both should be null for them to be the same
} else if (t1.val != t2.val) {
return false; // If the values are different, the trees are not the same
} else {
// Recursively check the left and right subtrees for sameness
return is_Same(t1.left, t2.left) && is_Same(t1.right, t2.right);
}
}

public static void main(String[] args) {
// Create two binary trees
TreeNode t1 = new TreeNode(1);
TreeNode t2 = new TreeNode(2);
TreeNode t3 = new TreeNode(3);
TreeNode t4 = new TreeNode(4);
t1.left  = t2;
t1.right = t3;

TreeNode n1 = new TreeNode(1);
TreeNode n2 = new TreeNode(2);
TreeNode n3 = new TreeNode(3);
TreeNode n4 = new TreeNode(4);
n1.left  = n2;
n1.right = n3;

// Check if n1 is a subtree of t1 and print the result
System.out.println(is_Subtree(t1, n1));
}
}

class TreeNode {
public int val;
public TreeNode left, right;

public TreeNode(int val) {
this.val = val;
this.left = this.right = null;
}
}
```
```

Sample Output:

```true
```

Flowchart: Java Code Editor:

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